vcl: remember graphic size after a threaded load

An Impress master slide with a bitmap background could turn plain
blue after saving and reopening the document. The saved styles.xml
still named the fill (for example draw:fill-image-name="Bitmap_20_2")
but held no draw:fill-image for it, so the reload fell back to the
default fill colour. The document had to stay idle long enough for its
images to be swapped out, which made the problem look intermittent.

Switching slides prefetches the page graphics with
GraphicFilter::MakeGraphicsAvailableThreaded, added in commit
8062e88e73 ("try to make available all slide images using threads")
with Change-Id Ifc39a2757834a9fb0dbafa61f13f5454e69af330. A text object
without a fill reports the page background there, so the master
background image is part of that prefetch. The loader hands the decoded
result to ImpGraphic::updateFromLoadedGraphic directly, which resets
mnSizeBytes to 0 and leaves the recalculation to swapIn, but swapIn
never runs on this path. The next memory trim then swapped the graphic
out with a size of 0. A swapped out graphic that is not prepared
answers GetSizeBytes from that value, so SvxUnoBitmapTable treated the
fill as empty and left it out of the export.

updateFromLoadedGraphic now measures the loaded content while it is in
memory, so the graphic keeps its size through the next swap out
whichever path loaded it, and the memory manager counts the real size.

Signed-off-by: Jaume Pujantell <jaume.pujantell@collabora.com>
Change-Id: Id472f542a531a1b9578322f3fdd12a8dd39843df
Reviewed-on: https://gerrit.collaboraoffice.com/c/online/+/13475
Tested-by: Jenkins CPCI <releng@collaboraoffice.com>
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
(cherry picked from commit 6a19f87f2430feacd16715947d385cee7e7c5a65)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/211533
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>
Tested-by: Jenkins

vcl/qa/cppunit/GraphicTest.cxx

@@ -1359,6 +1359,25 @@ CPPUNIT_TEST_FIXTURE(GraphicTest, testColorChangeToTransparent)
                          rBitmapAfter.GetPixelColor(410, 140));
 }
 
+CPPUNIT_TEST_FIXTURE(GraphicTest, testSwappedOutGraphicKeepsSizeAfterThreadedLoad)
+{
+    // Given a PNG graphic that was loaded once and then swapped out:
+    Graphic aGraphic = makeUnloadedGraphic(u"png");
+    CPPUNIT_ASSERT(aGraphic.makeAvailable());
+    CPPUNIT_ASSERT(aGraphic.ImplGetImpGraphic()->swapOut());
+
+    // When it is loaded again by the threaded loader and swapped out once more:
+    std::vector<Graphic*> aGraphics{ &aGraphic };
+    GraphicFilter::GetGraphicFilter().MakeGraphicsAvailableThreaded(aGraphics);
+    CPPUNIT_ASSERT(aGraphic.isAvailable());
+    CPPUNIT_ASSERT(aGraphic.ImplGetImpGraphic()->swapOut());
+
+    // Then it still reports its size, so it does not look like an empty graphic.
+    // Without the fix in place, this test would have failed, the graphic reported a size of 0
+    // bytes.
+    CPPUNIT_ASSERT(aGraphic.GetSizeBytes() > 0);
+}
+
 CPPUNIT_PLUGIN_IMPLEMENT();
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

vcl/source/gdi/impgraph.cxx

@@ -1412,6 +1412,10 @@ void ImpGraphic::updateFromLoadedGraphic(const ImpGraphic* pGraphic)
 
         mbSwapOut = false;
     }
+
+    // The loaded content is measured while it is in memory, so the graphic still knows its size
+    // after it is swapped out again.
+    ensureCurrentSizeInBytes();
 }
 
 void ImpGraphic::dumpState(rtl::OStringBuffer &rState)